1. Field of the Invention
This invention relates generally to the field of disc drive assemblies, and more particularly but not by way of limitation, to improvements in housings therefor which incorporate acoustic damping for reducing acoustic noise generated by disc drive assemblies.
2. Brief Description of the Prior Art
Disc drive assemblies of the type known as "Winchester" disc drive assemblies are well known in the industry. The archetype Winchester disc drive assemblies incorporated discs fourteen inches in diameter and were intended for use with large mainframe computers installed in specially constructed computer rooms in which environmental elements such as temperature and humidity could be controlled for optimum equipment operation. The users of such systems were typically located in locations far removed from the system and communicated with the system using keyboards and CRT displays, known in combination as remote terminals. Because only system maintenance and support personnel were required to work directly within the computer room, little consideration was given to acoustic noise generated by system elements such as cooling fans and disc drive motors.
However, with the advent of personal computers which are commonly located in home and office environments, acoustic noise generation has become a significant consideration in system design. In fact, in some marketplaces, particularly Europe, the amount of allowable acoustic noise in the workplace is strictly regulated by law.
With restrictions being placed on systems manufacturers, it has become common practice for manufacturers, which expect to sell their products multinationally, to analyze their intended market and specify their systems to meet the strictest requirements demanded in all target marketplaces.
Because most computer system manufacturers do not internally produce their own disc drive assemblies, but depend on specialized disc drive manufacturers, these system manufacturers have begun to strictly specify the amount of acoustic noise that the disc drive assembly itself can contribute to the overall system.
In disc drive assemblies of current technology, the major source of acoustic noise is sympathetic vibration of the disc drive housing caused by the spindle motor used to spin the discs or by the actuator used to move the read/write heads across the discs for data accesses. These disc drive assemblies are commonly in the form of a rectangular housing with a spindle motor and actuator motor mounted to one internal surface. Recent market demands for increased capacity, with accompanying increases in precision, have caused disc drive manufacturers to attach the shaft of the spindle motor and the pivot shaft of the rotary actuator motor to both the top and bottom of the disk drive housing. This has frequently resulted in housing surfaces vibrating at resonant frequencies that increase the total amount of acoustic noise.
Several approaches to acoustic noise reduction have been taken by disc drive manufacturers. Most involve the addition of compliant isolation devices between the noise source (the motors) and the external housing. However, such devices add expense to the design and require that space be set aside for them within the housing. With market trends toward increased capacity and smaller physical drive sizes, manufacturers have been understandably reluctant to allow room for these types of noise isolation devices in their designs.
Clearly, a need has long existed for an improved housing for disc drive assemblies for reducing acoustic noise generated by disc drive assemblies.